Lower Screed Interfaces

ABSTRACT

A screed assembly includes a screed assembly frame and a screed plate removably connected to the screed assembly frame to define a space between the screed assembly frame and the screed plate. A heating element and a hold down device for securing the heating element can be provided in the space between the screed assembly frame and the screed plate. The heating element is configured to be removed from the space by sliding the heating element out of the space and disengaging the heating element from the hold down device without removing the screed plate from the screed assembly frame.

TECHNICAL FIELD

This patent disclosure relates generally to asphalt paving machines and,more particularly, to various aspects of an electrically heated screedassembly.

BACKGROUND

The laying of asphalt paving material on road surfaces entails spreadingpaving material consisting of an aggregate filled bituminous mixture ona prepared roadbed. The paving material is spread while hot and is thencompacted so that upon cooling a hardened pavement surface is formed.Conventional paving machines utilize a heavy assembly termed a “screed”that is drawn behind the paving machine. The screed includes areplaceable screed plate that is constructed of a suitable steel, tospread a smooth even layer of paving material on the prepared roadbed.The weight of the screed assembly aids to compress the paving materialand perform initial compaction of the paving material layer. Screedassemblies can include vibratory mechanisms placed directly on thescreed plate or separate vibratory tamper bars connected in tandem withthe screed plate to aid in the initial compaction of the pavingmaterial.

To facilitate laying of the paving material, the screed is typicallyheated, to a temperature in the range of about 82° to 171° C. (180° to340° F.). Heating the screed assists the paving material in flowingunder the screed and reduces adhesion of the paving material to thescreed. If the screed is not adequately heated, the bituminous mixturecontacts the bottom of the screed and begins to harden, resulting inbuildup of paving material and excessive drag.

Conventional screed assemblies were commonly heated by fossil fuelpowered burners that heat the upper surface of the screed plate by thedirect application of flame or hot exhaust gases. More recently, screedassemblies with electrically powered heating elements are being used,wherein the heating elements are usually bonded or tightly secured to anupper surface of the screed plate.

For example, as shown in U.S. Pat. No. 5,417,516, a heated screedassembly for use with a paving machine includes a screed with anelastomeric, electrically-powered heating element carried on the uppersurface of the screed. To ensure that movement of the heating elementsalong a plane of the upper surface is substantially prevented duringoperation of the screed assembly, and to also ensure that the heatingelements stay in intimate contact with the screed while being vibratedduring operation, a layer of insulation is placed on top of the heatingelements and a retaining plate assembly, which is a heavy steel gridmember, is placed on top of the insulation to hold the heating elementsand the insulation in place. The design requires loose components placedon top of one another to maintain full contact of the heating elementswith the screed.

Screed assemblies by nature operate in an extremely abusive environmentthat may easily cause damage to or failure of key components. Theheating elements of a screed assembly are among the key components thatmay require repair or replacement. However, the heavy nature of theequipment involved and the design of conventional screed assembliesrequires that any such maintenance must normally be carried at a depotor shop location, for example, wherein the entire frame of the screedassembly must be disassembled in order to repair or replace themalfunctioning heating element. Furthermore, the use of multiple piecesto adequately hold down the heating elements in conventional screedassemblies adds to the time consuming and labor intensive process torepair or replace heating elements.

The present invention is directed to overcome one or more of theproblems as set forth above.

SUMMARY

The foregoing needs are met, to a great extent, by the disclosure,wherein in accordance with one embodiment a screed interface assemblyincludes a screed assembly frame, a screed plate removably connected tothe screed assembly frame to define a space between the screed assemblyframe and the screed plate, a heating element, and a hold down devicefor securing the heating element in the space, the heating elementconfigured to be removed from the space by sliding the heating elementout of the space and disengaging the heating element from the hold downdevice without removing the screed plate from the screed assembly frame.

In accordance with one embodiment a paving system for laying an asphaltpaving material includes a paving machine having an engine and apropelling arrangement, and a screed assembly attached to the pavingmachine, wherein the screed assembly has a screed assembly frame, ascreed plate removably connected to the screed assembly frame to definea space between the screed assembly frame and the screed plate, aheating element, and a hold down device for securing the heating elementin the space, the heating element configured to be removed from thespace by sliding the heating element out of the space and disengagingthe heating element from the hold down device without removing thescreed plate from the screed assembly frame.

In accordance with one embodiment a method of removing a heating elementfrom a screed assembly having a screed plate coupled to a screedassembly frame includes disengaging the heating element from a hold downdevice by sliding the heating element out of a space defined between thescreed plate and the screed assembly frame while maintaining thecoupling of the screed plate to the screed assembly frame.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a paving machine with a screed assembly, inaccordance with aspects of the present disclosure;

FIG. 2 is a plan view of a screed assembly, in accordance with aspectsof the present disclosure;

FIG. 3 is a close up perspective view of a screed assembly, inaccordance with aspects of the present disclosure;

FIG. 4 is another close up perspective view of a screed assembly, inaccordance with aspects of the present disclosure;

FIG. 5 is a perspective view of a screed plate, in accordance withaspects of the present disclosure;

FIG. 6 is a perspective view of a screed plate with a plurality ofheating elements, in accordance with aspects of the present disclosure;

FIG. 7 is a perspective view of a screed plate with a plurality ofheating elements and various hold down devices, in accordance withaspects of the present disclosure;

FIG. 8 is another close up perspective view of a screed assembly, inaccordance with aspects of the present disclosure;

FIG. 9 is a perspective view of a screed plate configured foraccommodating a single heating element, in accordance with aspects ofthe present disclosure;

FIG. 10 is a perspective view of the screed plate of FIG. 9 with aheating element, in accordance with aspects of the present disclosure;

FIG. 11 is a perspective view of the screed plate of FIG. 9 with aheating element and various hold down devices, in accordance withaspects of the present disclosure; and

FIG. 12 is a side view of the screed plate of FIG. 9, in accordance withaspects of e present disclosure.

DETAILED DESCRIPTION

The disclosure will now be described with reference in the drawingfigures, in which like reference numerals refer to like partsthroughout.

Various aspects of the lower screed interfaces may be illustrated bydescribing components that are connected, attached, and/or joinedtogether. As used herein, the terms “connected”, “attached”, and/or“joined” are used to indicate either a direct connection between twocomponents or, where appropriate, an indirect connection to one anotherthrough intervening or intermediate components. In contrast, if acomponent is referred to as being “directly coupled”, “directlyattached”, and/or “directly joined” to another component, there are nointervening elements present.

Embodiments of the disclosure advantageously provide systems and methodsfor using lower screed interfaces. The lower screed interfaces describedherein provide advantages for the repair and/or replacement of componentparts of a screed assembly in a paving machine in a safe and effectivemanner. The systems and methods described herein are applicable for usewith paving machines and, in particular, paving machines that use aheavy screed assembly drawn behind the paving machine for heating andshaping the asphalt to form the road service.

Referring to the drawings, specifically FIG. 1, an asphalt pavingmachine 10 is shown with a screed assembly 12 attached to the backthereof. The asphalt paving machine 10 is supported by a propellingarrangement 14 that is driven by an engine 16 in a conventional manner.

In accordance with aspects of the disclosure, the screed assembly 12 maybe pivotally connected behind the asphalt paving machine 10 by tow arms18. The screed assembly 12 may be any of a number of configurations suchas a fixed width screed or a multiple section screed that includesextensions. As shown in FIG. 2, the screed assembly 12 may be providedwith a main screed section 20 having a left screed section 22 and aright screed section 24, for example. The left and right screed sections22, 24 may be hingably connected to one another along a longitudinalcenterline 26 so that various operations, such as crowning, can beperformed. A screed extension 28 may also be provided behind andadjacent to both the left and right screed sections 22,24. It shouldalso be understood that screed extensions 28 may be positioned in frontof the main screed section 20 without departing from the gist of thepresent invention. Screed extensions 28 are slidably movable, such as byactuators (not shown), so that varying widths of paving material can belaid. The screed assembly 12 may also include a tamper bar arrangement29 positioned forward of the main screed section 20, as shown in FIGS. 1and 2. Alternatively, some screed assemblies 12 include a vibratorymechanism (not shown) positioned above the left and right screedsections 22,24 and the screed extensions 28 to aid in the initialcompaction of the paving material being laid down.

Referring to FIGS. 2 and 3, each of the screed sections 22, 24, 28 mayinclude a screed plate 30 that is removably connected to and supportedby a frame 32. End plates 34 (see FIG. 4) may provide reinforcement tothe frame 32. The frame 32 may integrally form an external housing, oran external housing may be mounted to the frame 32, to provideprotection of the internal components of the screed assembly 12 from theharsh operating environment. In accordance with other aspects of thepresent invention, access panels, for example, may be configured intothe housing to provide efficient access to the internal components ofthe screed assembly 12.

As shown in FIGS. 3 and 4, the screed plate 30 may have a forwardleading edge 38, a rearward trailing edge 42, and define an uppersurface 46 and a lower surface 48 extending between the leading edge andthe trailing edge 42. As used herein, “forward” generally refers to theportion of the screed assembly 12 that faces the asphalt paving machine10, while “rearward” refers to the portion distal from the asphaltpaving machine 10. In use, the screed assembly is pulled behind theasphalt paving machine 10 so that the paving material is fed under thescreed plate 30.

Each screed plate 30 in the screed assembly 12 is heated by a screedheating assembly that may include one or more removable heating elements50 electrically coupled to a junction box 52. The heating elements 50may be resistive type heating elements having leads 54 for connecting tothe junction box 52.

The junction box 52 may be mounted to the frame 32 and electricallycouple to an electric power supply 64 (see FIG. 1), which may include anelectric generator 66, for example, that is operatively connected to theengine of the asphalt paving machine 10. The generator 66 may, forexample, be an AC or DC generator such as a 12 or 24 volt DC or 110 or240 AC generator. The output connections of the power supply 64 may bewired into the junction box 52 of the heating assembly. In accordancewith certain aspects of the present disclosure, military styleconnectors 53 may be used to complete the electrical circuit between theleads 54 of the heating elements 50 and the output connections of thepower supply 64. For example, the leads 54 may each have a male militarystyle pin connector 55 that mates with a female military style socketconnector 56 extending from the junction box 52. The connectors 55 and56 may be secured together by a locking mechanism, such as a threadedlocking nut, to prevent disengagement during the harsh operatingconditions and extensive vibrations experienced by the screed assembly12.

As shown in FIGS. 3 and 4, the frame 32 defines a space 70 when mountedto the screed plate 30. In accordance with aspects of the presentinvention, the heating elements 50 may slide into and/or out of thespace 70 for easy and efficient installation, removal and/or replacementwith minimum manipulation of parts and without the entire disassembly ofthe frame 32 from the screed plate 30.

Accordingly, FIGS. 5-7 illustrate aspects of a heating assembly for usein heating the screed plate 30. As shown in FIG. 5, the screed plate 30,which may be a substantially flat metal plate, is configured with anetwork of frame posts 72. The frame posts 72 may be situatedsubstantially toward peripheral portions of the screed plate 30, forexample, and are of predetermined length to extend through correspondingopenings 74 in the frame 32 (see FIG. 3). The frame posts 72 may beformed with external threading, for example, and fasteners, such aswashers and nuts, may be used to secure the screed plate 30 to the frame32. via the frame posts 72.

One or more heating elements may be configured for positioning on theupper surface 46 of the screed plate 30. In particular, as shown in FIG.6, a first heating element 80 and a second heating element 90(collectively heating elements 50 as described above) may besubstantially flat elongated conducting elements formed to slide intothe space 70 as illustrated FIGS. 3 and 4 (e.g., the direction indicatedby the arrows in FIG. 6).

The first heating element 80 may be configured in an extended L shape,comprising a longitudinal run 82 and a shorter terminal run 84. Thelongitudinal run 82 may extend substantially an entire transversedimension of the screed plate 30 from the shorter terminal run 84 of theheating element 80 to a distal end 83. The shorter terminal run 84 maybe arranged to extend in a substantially planar manner perpendicularlyfrom the longitudinal run 82. A positioning post 86 may be formed at anend of the terminal run 84 that rises substantially vertically andpermits coupling to or extension of a lead 54. The configuration of thefirst heating element 80, in combination with the positioning of theframe posts 72, allows efficient placement and positioning of theheating element 80 into the screed assembly 12 without removal of theframe 32 even when it may be difficult to see into the space 70 intowhich the heating element 80 is being inserted.

The heating element 80 described above is configured to slide into thespace 70 by insertion of the distal end 83 between the forward portionof the frame 32 and the frame posts 72. The longitudinal run 82 ispositioned forward of the frame posts 72, parallel to and nearlyabutting the forward leading edge 38 of the screed plate 30. Referringback to FIG. 3, the frame 32 may be provided with notches 33corresponding to the positioning post 86, The notches 33 and positioningpost 86 provide visual indications for efficient alignment andpositioning of the heating element 80 during insertion.

To maximize heat transfer from the heating element 80 to the screedplate 30, a number of hold down devices may be provided to easily andefficiently secure the heating element 80 with maximum surface contactbeing maintained between the heating element 80 and the upper surface 46of the screed plate 30. For example, as shown in FIG. 7, a hold downclamp 87 may be provided to secure the distal end 83 of the heatingelement 80. The hold down clamp 87 may be coupled to the screed plate bya suitable securing means, and comprise a metal T-plate having rampedarms for receiving the distal end 83 of the heating element 80. Theramped arms of the hold down clamp 87 allow the distal end 83 to beeasily accepted when sliding into position while progressively applyingincreased downward pressure until the distal end 83 is in a finalposition and firmly secured by the full holding force of the hold downclamp 87.

In accordance with yet other aspects of the present disclosure, bobbins88 may be used to provide periodic holding forces along the longitudinalrun 82 of the first heating element 80. Each bobbin 88 may be configuredwith a lower flanged portion 89 and be formed to slidably mount onto theframe posts 72. Referring back to HG. 3, the bobbins 88 may beconfigured to extend through the openings 74 (refer to FIG. 3) in theframe 32. Thus, when the frame 32 is secured to the screed plate 30 viaa securing device 100, such as lock nut assembly or a washer and nutassembly, as shown in FIG. 8, the bobbins 88 may be forced downward. Thelower flanged portions 89 of the bobbins 88 are pressed against theheating element 80 to secure the heating element 80 in position and inconstant contact with the upper surface 46 of the screed plate 30.

To release the holding force, the pressure being exerted by each bobbin88 may be released by loosening the securing devices 100. Thus theholding forces applied by the bobbins 88 may be quickly and easilyreleased without having to completely remove the screed plate 30 fromthe frame 32. Rather, the securing devices 100 are simply loosened toallow the bobbins 88 to release enough holding force so that the firstheating element 80 may slide out from the space 70. A new heatingelement 80 may then be inserted into the space 70 so that thelongitudinal run 82 slides under the flanged portions 89 of the bobbins88 until the distal end 83 of the new heating element is captured underthe hold down clamp 87, for example. Tightening of the securing devices100 on the frame posts 72 then provides the holding pressure against thebobbins 88 to securely hold the heating element 80 via the flangedportions 89.

With the skin temperature of the heating element 80 reaching 600°-700°F., maximum surface contact of the heating element 80 with the screedplate 30 near the leading edge 38 ensures that the leading edge 38 andforward surface areas of the lower surface 48 of the screed plate 30 areeffectively heated. The asphalt paving material is prevented fromcooling upon contact with the leading surfaces of the screed plate 30,preventing hardening and caking of the paving material on the screedplate 30 for maintaining a smooth paving surface as the screed plate 30moves over the asphalt paving material.

Referring again to FIG. 6, the second heating element 90 may be insertedrearward of the first heating element 80 for heating the remainder ofthe screed plate 30. The second heating element 90 may be substantiallyrectangular in form with two parallel longitudinal runs 92 and twoparallel transverse runs 94. A positioning post 96 may be formed at anend of one of the transverse runs 94, the positioning post 96 risingsubstantially vertically and permitting coupling of the second heatingelement to or extension of a lead 54. The configuration of the secondheating element 90, in combination with the positioning of the frameposts 72, allows efficient placement and positioning of the heatingelement 90 into the screed assembly 12 without removal of the frame 32even when it may be difficult to see into or access the space 70 intowhich the heating element 90 is being inserted. Referring back to FIG.3, the frame 32 may be provided with notches 33 for positioning thepositioning post 96.

For example, the heating element 90 described above is configured toslide into the space 70 so that one of the longitudinal runs 92 issituated toward the rearward arranged frame posts 72 and the other ofthe longitudinal runs 92 is situated toward the center of the screedplate 30. With the skin temperature of the heating element 90 reaching600°-700° F., maximum surface contact of the heating element 90 isprovided to effectively heat the remaining portions of the screed plate30 not heated by the first heating element 80. The asphalt pavingmaterial is also prevented from cooling upon contact with the trailingsurfaces of the screed plate 30, preventing adherence of the pavingmaterial on the screed plate 30 and allowing a smooth paving surface tobe formed as the screed plate 30 moves over the asphalt paving material.

To maximize heat transfer from the heating element 90 to the screedplate 30, a number of hold down devices may be provided to easily andefficiently secure the heating element 90 with maximum surface contactbeing maintained between the heating element 90 and the screed plate 30.For example, as shown in FIG. 7, a hold down webbing 97 may be providedto secure the second heating element 90 in place. The hold down webbing97 may be made from any suitable material, such as steel, aluminum, or ahigh-temperature carbon fiber composite, for example, and is configuredto be lightweight and strong. The hold down webbing 97 may comprise asubstantially longitudinal body 98 with extension arms 99 havingslightly curved distal ends configured to straddle and hold the parallellongitudinal runs 92 at predetermined points. The hold down webbing 97may be removable with the heating element 90 or may be configured toremain in the space 70 in the frame 32 during removal and/or insertionof the heating element 90. Securing devices, such as bolts and/orholding pockets built into the frame 32 may be used to hold the webbing97 in the space 70.

The frame 32 may be configured so that hold down bolts 102, such asthose shown in FIG. 8, may be used to apply downward pressure againstthe hold down webbing 97. The hold down bolts 102 may have distal ends,for example, designed to abut against the longitudinal body 98 of thewebbing 97 in order to apply pressure against the webbing 97 whentightened. The pressure applied by tightening the hold down bolts 102 isdistributed throughout the webbing 97 and, in particular the extensionarms 99, to secure and hold the second heating element 90 in positionwith a maximum surface area of the heating element 90 pressed againstthe screed plate 30. In accordance with yet other aspects of the presentdisclosure, the hold down bolts 102 may be configured to be externallyaccessible for a technician working on the assembly. For example, thebolts may extend from the frame 32 in a manner that permits a technicianto easily access the hold down bolts 102 without having to remove ormove components, or without having to feel around in a blind cavity tolocate and attempt to tighten or loosen the bolts.

As is described in more detail below with respect to yet anotherembodiment of the present disclosure, the webbing 97 may be configuredwith one or more slight longitudinal bends provided toward the middle ofthe longitudinal body 98. The bend(s) may form a 3-5° angle with a planeparallel to the screed plate 30, for example, to provide an increasedlateral stiffness to the webbing 97 (see, e.g., FIG. 12). Accordingly,when the hold down bolts 102 are tightened to apply pressure against thelongitudinal body 98, the webbing 97 distributes the force downwardunder the pressure to apply a holding force against the longitudinalruns 92. Although described above with a bend of 3-5°, any suitable bendfrom 1-15° may be used to provide increased lateral stiffness to thewebbing 97. The external accessibility of the hold down bolts 102 mayfurther enhance the ability of a technician to easily release and/orapply the downward pressure of the hold down bolts against the webbing97. Exchange and/or maintenance of the heating elements in the field isthus greatly enhanced.

In accordance with yet other aspects of the present disclosure, FIGS. 9and 10 illustrate a screed plate 30 in which the frame posts 72 may bearranged to accommodate insertion of a one-piece heating element 180,for example. The heating element 180 may be configured in asubstantially planar S-shaped configuration defined by three parallellongitudinal runs 182 extending substantially the entire transversedimension of the screed plate 30 and connected by U-shaped bends, adistal end 183, and a terminal end 184 that runs substantiallyperpendicular to the direction of the longitudinal runs 182. Theterminal end 184 may be configured to have a positioning post 186 thatrises substantially vertically and permits coupling to or extension of alead 54.

The configuration of the one-piece heating element 180, in combinationwith the positioning of the frame posts 72, allows efficient placementand positioning of the heating element 180 into the screed assembly 12without removal of the frame 32 even when it may be difficult to seeinto or access the space 70 into which the heating element 180 is beinginserted.

The heating element 180 described above is configured to slide into thespace 70 so that the distal end 183 slides between the frame posts 72and the forward portion of the frame 32. The forward longitudinal run182 with distal end 183 may thus be positioned forward of the frameposts 72, parallel to and nearly abutting the forward leading edge 38 ofthe screed plate 30. Referring back to FIG. 3, the frame 32 may beprovided with notches 33 for positioning the positioning post 186. Thenotches 33 and positioning post 186 provide visual indications forefficient alignment and positioning of the heating element 180 duringinsertion.

To maximize heat transfer from the heating element 180 to the screedplate 30, a number of hold down devices may be provided to easily andefficiently secure the heating element 180 with maximum surface contactbeing maintained between the heating element 180 and a upper surface 46of the screed plate 30. For example, as shown in FIG. 11, a hold downclamp 187 may be provided to secure the distal end 183 of the heatingelement 180. The hold down clamp 187 may be coupled to the screed plate30 by a suitable securing means, and comprise a metal T-plate havingramped arms for receiving the distal end 183 of the heating element 180.The ramped arms of the hold down clamp 187 allow the distal end 183 tobe easily accepted when sliding into position while progressivelyapplying increased downward pressure until the distal end 183 is in afinal position and firmly secured by the full holding force of the holddown clamp 187.

In accordance with yet other aspects of the present disclosure, a holddown webbing 190 may be provided to secure the one-piece heating element180 in place. Although described herein with reference to a one-pieceheating element 180, the webbing 190 may be used with a variety of otherconfigurations of heating elements, including a plurality of heatingelements. The hold down webbing 190 may be made from any suitablematerial, such as steel, aluminum, or a high-temperature carbon fibercomposite, for example, and is configured to be lightweight and strong.The hold down webbing 190 may comprise a substantially longitudinal body191 with extension arms 192 having slightly curved distal endsconfigured to straddle and hold the heating element 180. A holding rail194 may be provided to further assist in positioning and holding downthe forward longitudinal run 182 of heating element 180.

In accordance with yet other aspects of the present disclosure, as shownin FIGS. 11 and 12, the hold down webbing 190 may be configured with aplurality of studs 196 that extend from a central portion of thelongitudinal body 191. At least some of the studs 196 extend through theframe 32, effectively positioning the hold down webbing 190 relative tothe frame 32. Biasing devices 200, which may be wave springs sandwichedbetween two spring plates, for example, may be mounted on the studs 196and used to apply variable downward pressure against the hold downwebbing 190. The biasing devices 200 may be situated such that when theframe 32 is in place and secured, the biasing devices 200 are compressedbetween the frame 32 and the hold down webbing 190. The biasing devices200 may thus exert a downward pressure against the hold down webbing 190such that the heating element 180 is secured. The biasing devices 200maintain a distributed pressure against the webbing 190 during use ofthe screed assembly yet provide enough flexibility for the easy removaland/or insertion of the heating element 180 secured underneath thewebbing 190. As is illustrated inn FIG. 12, the webbing 190 may beconfigured with a slight bend θ (e.g., 3°-5°) from parallel with thescreed plate 30 along one or more portions of the longitudinal body 191when viewed from a side. The bends may provide a slight elevation to thebody 191 and provide an increased lateral stiffness to the webbing 190while ensuring an even lateral distribution of pressure, for example, tosecure and maintain the position of the heating element 180 against thescreed plate 30. Although described above with a bend of 3-5°, anysuitable bend from 1-15° may be used to provide increased lateralstiffness to the webbing 97.

With the skin temperature of the heating element 180 reaching 600°-700°F., maximum surface contact of the heating element 180 with the uppersurface 46 is provided near the leading edge 38 and generally along allportions of the screed plate 30. The asphalt paving material is thuseffectively prevented from cooling upon contact with the leadingsurfaces of the screed plate 30, preventing hardening of the pavingmaterial on the screed plate 30 and allowing a smooth paving surface tobe formed as the screed plate 30 moves over the asphalt paving material.In addition, direct heat transfer to the frame 32 may be reduced throughthe configuration described herein.

INDUSTRIAL APPLICABILITY

The disclosure includes a system and methods for effectively holdingdown heating elements during operational use of a heated screed plateassembly while providing an efficient configuration for easily removingand/or replacing the heating elements without having to disassemble thescreed plate assembly. The lower screed interfaces disclosed are for useon an asphalt paving machine.

The many features and advantages of the disclosure are apparent from thedetailed specification, and, thus, it is intended by the appended claimsto cover all such features and advantages of the disclosure which fallwithin the true spirit and scope of the disclosure. Further, sincenumerous modifications and variations will readily occur to thoseskilled in the art, it is not desired to limit the disclosure to theexact construction and operation illustrated and described, and,accordingly, all suitable modifications and equivalents may be resortedto that fall within the scope of the disclosure.

We claim:
 1. A screed interface assembly comprising: a screed assemblyframe; a screed plate removably connected to the screed assembly frameto define a space between the screed assembly frame and the screedplate; a heating element; and a hold down device for securing theheating element in the space, the heating element configured to beremoved from the space by sliding the heating element out of the spaceand disengaging the heating element from the hold down device withoutdisengaging the screed plate from the screed assembly frame.
 2. Theassembly of claim 1, wherein the screed plate comprises a leading edge,a trailing edge, an upper surface extending between the leading edge andthe trailing edge, and frame posts extending from the upper surface formounting the screed plate to the screed assembly frame.
 3. The assemblyof claim 2, wherein the heating element is a substantially flatelongated conducting element having a longitudinal run, the longitudinalrun having a distal end and extending substantially an entire transversedimension of the screed plate.
 4. The assembly of claim 3, wherein theheating element further comprises a shorter run configured to extendperpendicularly from the longitudinal run, the shorter run having apositioning post formed at a free end that rises orthogonally from aplane containing the longitudinal run.
 5. The assembly of claim 4,wherein the screed assembly frame is configured with at least one notchand the positioning post aligns with the notch when the heating elementis positioned in the space.
 6. The assembly of claim 3, wherein the holddown device is a metal T-plate having ramped arms for receiving andsecuring the distal end of the longitudinal run.
 7. The assembly ofclaim 6, further comprising a second hold down device.
 8. The assemblyof claim 7, wherein the second hold down device is a metal webbinghaving a longitudinal body portion and a plurality of extension armsconfigured to straddle and secure the heating element.
 9. The assemblyof claim 8, further comprising hold down bolts, wherein the hold downbolts are mounted through the assembly frame and apply a distributedpressure against the heating element via the metal webbing.
 10. Theassembly of claim 7, wherein the second hold down device is a bobbinmounted on one of the framing posts, the bobbin having a lower flangeportion for securing the heating element at a select location along thelongitudinal run.
 11. The assembly of claim 8, wherein the metal webbingincludes a stud that extends from the longitudinal body portion of themetal webbing and the screed frame assembly includes a hole forreceiving the stud therethrough.
 12. The assembly of claim 11, furthercomprising a biasing device mounted on the stud for biasing the metalwebbing toward the screed plate when the screed plate is secured to thescreed frame assembly.
 13. The assembly of claim 12, wherein the biasingdevice is a wave spring sandwiched between two spring plates forproviding a variable applied force against the metal webbing.
 14. Theassembly of claim 1, further comprising a junction box mounted to thescreed frame assembly and electrically coupled to an electric powersupply.
 15. The assembly of claim 14, further comprising a leadextending from the heating element and a military style connectionincorporated into the junction box for completing the electrical circuitbetween the lead and the electric power supply.
 16. A paving system forlaying an asphalt paving material, comprising: a paving machine havingan engine and a propelling arrangement; and a screed assembly attachedto the paving machine, the screed assembly including: a screed assemblyframe; a screed plate removably connected to the screed assembly frameto define a space between the screed assembly frame and the screedplate; a heating element; and a hold down device for securing theheating element in the space, the heating element configured to beremoved from the space by sliding the heating element out of the spaceand disengaging the heating element from the hold down device withoutdisengaging the screed plate from the screed assembly frame.
 17. Thepaving system of claim 16, wherein the hold down device is a metalwebbing having a longitudinal body portion and a plurality of extensionarms configured to straddle and secure the heating element.
 18. Thepaving system of claim 16, wherein the hold down device is a bobbinhaving a lower flange portion for securing the heating element at aselect location
 19. A method of removing a heating element from a screedassembly, the screed assembly comprising a screed plate coupled to ascreed assembly frame, the method comprising: disengaging the heatingelement from a hold down device by sliding the heating element out of aspace defined between the screed plate and the screed assembly framewhile maintaining the coupling of the screed plate to the screedassembly frame.
 20. The method of claim 19, further comprising:disconnecting the heating element electrically connected to a junctionbox via a military style connection.